The invention relates to an aqueous, colloidal gas black suspension, to a process for its production and to its use.
It is known to use aqueous, colloidal carbon black suspensions to produce paints, printing inks or else directly as inks, for example in ink jet printers (U.S. Pat. No. 5,085,698, U.S. Pat. No. 5,320,668).
It is also known to produce carbon black suspensions using dyes which also act as wetting agents without the addition of further wetting agents (U.S. Pat. No. 6,503,317) (PCT/US99/11935).
It is also known to produce aqueous carbon black suspensions using water-soluble wetting agents, for example acrylic resins (U.S. Pat. No. 5,609,671) or ethoxylates (DE 19824947 A1).
EP 1215250 discloses ink jet inks which contain a solvent, a pigment and also a dye which is soluble in the solvent, of which the absorption peak is in the wavelength range of 500 nm to 700 nm.
Drawbacks of the known wetting agent-stabilised carbon black suspensions are, when using non-ionogenic surfactants, the excessively high zeta potential and the low surface tension and, when using anionic surfactants, excessive wetting of the paper owing to the pronounced interactions with the likewise anionic paper coating, and these lead to low optical printing densities.
Further drawbacks of the known dye-stabilised carbon black suspensions are the inadequate stability in storage and freeze-thaw stability. With relatively long service lives of the dispersions or at storage temperatures of more than 50° C. or less than 0° C., this leads to a marked and irreversible increase in the viscosity, to reagglomeration of the suspended pigment particles or to complete flocculation of the suspension. Ink jet prints with known dye-stabilised carbon black dispersions also exhibit insufficient water resistance, and this is a significant drawback in terms of application technology. When using furnace carbon blacks a relatively low optical density is also seen.